Aging infrastructure is a prime concern in the water and wastewater world. Municipalities in many countries now do face a gigantic task: Many pipes are nearing the end of their life spans, and the time to choose a replacement has arrived. In a long-term project like pipe replacement, where life span can exceed 100 years, proper material choice is critical. This is the first part discussing the most common types of municipal pipe materials, along with their strengths, weaknesses and uses.
Ductile Iron Pipe
It’s used to be called cast iron pipe. Its longest life span can reach 100 to 150 years. The pipe’s materials are 95 percent recycled, which is the best advantage in the buried infrastructure industry.
Despite its strength, ductile pipe is subject to corrosion from aggressive environments caused by acids, either in the interior of the pipe from acidic sewage materials or on the exterior from acidic soil conditions. To combat the problem in water service, the inside of the pipe is lined with a cement mortar lining, which protects the pipe and forms a barrier. Sewers can be a little more challenging for ductile iron, so a special internal pipe lining is sometimes needed.
Vitrified clay pipe is highly corrosion resistant. The only chemical known to affect clay pipe is hydrofluoric acid, which is not likely to be found in sanitary sewers.
Clay pipe is valued for its longevity, corrosion-resistant properties and sustainability. However, it also has some limitations: It is typically limited to gravity-flow applications, and the maximum pipe length is 10 feet due to the kiln firing process.
There is hardly criticisms on the HDPE pipe, a new alternative to traditional metal pipes. The high-density polyethylene performs well in corrosive conditions and boasts a low failure rate.
Another shining point of HDPE is that it’s almost the first choice in municipal pipe material in earthquake-prone areas. A study in the 2010 Chile earthquake showed that“while the rest of the water system suffered thousands of damaged pipes, no HDPE pipe was damaged.”
The only worry about HDPE should be its abuse. After all, this pipe is made of plastic. In long-term projects, the recyclability should be seriously considered.